I just released version 1.9 of my Email Log WordPress plugin. This released fixed an issue with pagination while viewing log files and various improvements at code level.

About Email Log WordPress plugin

Email Log is a WordPress plugin that allows you to log every email sent through WordPress and provides a UI where you can view them. The logged emails can be searched based on date, email address or subject.

As I promised in my year end review post, I have started working on my WordPress plugins. My Easy Retweet WordPress plugin badly needed an update to fix a couple of warnings and I just released v3.1 of the plugin with a couple of fixes and some new features.

New Twitter Backend

Instead of rewriting the entire Twitter backend again, I am not using the excellent wp-twitter-api, provided by @timwhitlock which allows you to easily communicate with Twitter API from your WordPress plugin.

If you are a WordPress plugin developer and want to communicate to the Twitter API from your WordPress plugin, then I would highly recommend you to use wp-twitter-api, instead of creating your own.

Setting up Twitter App

The new version of the Twitter API needs you to make authenticated calls even to get some basic information about a twitter screen name. So after you installed the plugin you need to follow these steps so that the plugin could interact with the Twitter API.

Creating tables in Single site installations

Before we get into WordPress Multisite, first let’s see how we can create a table in a single site WordPress installation. You have to hook into the register_activation_hook action, which will be called every time you activate your plugin and then check if your table exists or not. If it doesn’t exist, then you can create your table.

The above code will work even in WordPress Multisite installations, if your plugin will be activated individually for each blog. But if your plugin is networked activated, then the above code will create the table only for the primary blog.

Creating tables for all blogs in a WordPress Multisite installation

Now that we know how to create the table for a single blog, let’s see how we can create the table for all the blogs in a WordPress Multisite installation. Even in this case, we have to hook into the same register_activation_hook action, but should loop through all the blogs in the network.

Creating table when a new blog is created

The above code will create the table only for the blogs that were created before the plugin got network activated. We should also make sure that we create the table for every new that gets created. In order to do that we can hook into the wpmu_new_blog action.

Querying the correct table

When we are querying the table, we should always use $wpdb->prefix . $table_name. If we do that, then WordPress will automatically query the correct table based on the current blog. We don’t have to manually find out the blog id and add it to the table name.

Now your plugin should be completely compatible with WordPress Multisite 🙂

Alternate approach

If you look into the above code closely, you will notice that we are creating one table for each blog in the network. For most WordPress Multisite installations, this shouldn’t be a problem. But some WordPress Multisite installation may have thousands and even hundreds of thousands of blogs. In those cases, we might end up creating huge amount tables which might become a bottleneck. Also my plugin needed just one table. Some plugins might need more than one table, which might also increase the number of tables that gets created.

One alternate approach is to create just one table for all blogs and then separate out data for each blog using a blog_id column. While querying the table, we can filter out based the blog_id column.

If I had started my plugin from scratch, I would have done that instead of creating separate tables.

Update: As Damian pointed out below in the comments, if you are using this approach, then you used use $wpdb->base_prefix to get the main prefix and not the individual sites prefix.

Removing the tables when the plugin is deleted

The other thing to keep in mind is that we should delete all the tables when the plugin is deactivated and deleted. I will write a separate article explaining how we should do that.

With WordPress Multisite becoming more popular these days, I hope this information was useful to you. Do let me know if you have any question or comments. Also you can checkout the entire code of my Email Log plugin in github.

I just released version 1.7 of my Email Log WordPress plugin, which adds full compatibility with WordPress Multisite.

About Email Log WordPress plugin

Email Log is a WordPress plugin that allows you to log every email sent through WordPress and provides a UI where you can view them. The logged emails can be searched based on date, email address or subject.

WordPress Multisite compatibility

Earlier versions of Email Log plugin had some compatibility with WordPress Mu (older version of multisite), but I didn’t test it for long time. Also when WordPress Mu got merged into WordPress core, certain things have changed and my plugin was not fully compatible after that.